Materials:

Transmitter-It is used to transmit the radio wave to the receiver. There are many kinds of transmitter circuit; I tried to choose some circuit with simple linking and small in size. Mostly, each of the circuit must be included the trimmer, microphone, resistors, IC, cab, copper wire, antenna. Each circuit provide different radio wave frequency, the unit is MHz. There are 2 circuits I’ve found from the web site (refer to Appendix1), and in the beginning I choose one of these circuits, this is the first circuit I tried to use in this project; unluckily there are some components cannot be found and I only gave up this circuit. The second transmitter is the miniature FM transmitter. (the detailed information would be mentioned in the next section), the frequency range is 90-94MHz with 9V supply and distance range is about 30m. This circuit didn’t work probably also and I only gave up then. Now I am trying the third circuit, it is much workable than both of the circuits before.

Receiver-In the beginning, I decide to use the FM radio as my receiver.

I need to tune the radio to the acceptance MHz and receive the signal. However, it cannot get a satisfied result for there are many interruptions. Lastly, I try to use an independent receiver circuit.

Battery- The battery must be small in size, there are many different kinds of battery such as the button cell (1.5v) and the lithium (3v). In this moment, it does not have decision in battery chosen; the last decision depends on the voltage it needs to use.